The present invention relates to a rotatable drilling head normally utilized in underground mining operations for cutting particles of a material, for example, coal, from a seam of such material so as to remove it from the mine. The rotatable drilling head according to the present invention provides a cylindrical drum having a front end and an open rear end and defines an interior cavity. On the exterior circumferential surface of the drum, a first spiral is outwardly projected which is disposed in a manner to forwardly advance coal particles between adjacent convolutions thereof. In advance of the drum there is provided a cutting bit for cutting into the coal seam.
Between the cutting bit and the front end of the drum, there is provided a nose spiral which gradually tapers having its successive convolutions increasing in radial dimension as the nose spiral extends between the cutting bit and the front end of the drum. The nose spiral is arranged so that coal particles can be rearwardly advanced thereby. Rigidly carried on the interior of the drum is an interior spiral which extends substantially the entire length of the drum. The direction of the convolutions of the interior spiral is such that the coal particles are rearwardly advanced through the interior of the drum.
The nose spiral and the exterior spiral terminate with each other and together define at least one recovery aperture through which the mined coal particles forwardly advancing by virtue of the exterior spiral and rearwardly advancing by virtue of the nose spiral can pass therethrough to the interior cavity of the drum.
Conventional rotatable drilling heads are provided with a spiral which is arranged in a direction so that the mined particles can only be directed rearwardly relative to the direction of advance of the drilling head into a seam of coal. It has been proposed, however, to provide a drum partially surrounding the single direction spiral as evidenced by U.S. Pat. No. 2,562,841 to Compton and U.S. Pat. No. 2,770,449 to McCarthy. These two prior art references also disclose that an exterior spiral arranged upon the partial drum assembly can be utilized to similarly rearwardly advance the coal. Thus, the prior art drilling heads only contemplate that dual spirals can be provided so that the interior and exterior direction of movement of coal particles is towards the rear of the drilling head.
According to the present invention there is provided a novel rotatable drilling head which generally utilizes three distinct spiral arrangements for drilling and removing coal particles from a seam of coal. The first spiral is arranged on the exterior circumferential surface of a drum while the second spiral is arranged on the interior surface of the drum. Each spiral preferably extends the entire length of the drum. The exterior spiral is arranged in such a manner that rotational movement of the drum encourages coal particles to be forwardly advanced while the interior spiral is arranged so as to encourage the coal particles to be rearwardly advanced. At the front end of the drum, there is provided an additional spiral called herein the nose spiral. The nose spiral gradually tapers so that its largest dimension is adjacent the front end of the drum while the smallest dimension occurs at the cutting bit. The direction of the convolutions of the nose spiral are such that the mined coal particles are encouraged to move rearwardly.
At the front end portion of the drum, the exterior spiral and the nose spiral intercept one another and together define at least one recovery aperture through which the mined coal particles which are being forwardly advanced by virtue of the exterior spiral and rearwardly advanced by virtue of the nose spiral can pass therethrough and be accepted into the interior cavity of the drum. Once the coal particles have passed through the recovery aperture, they are encouraged to rearwardly advance in the interior of the drum by virtue of the interior spirals. The open rear end of the drum permits the coal particles to be removed from the mine by any conventional means such as, for example, conveyors, or the like.
According to another aspect of the present invention a flexible spiral can be provided intermediate adjacent convolutions of the exterior spiral. The flexible spiral is preferably composed of a durable, yet flexible, synthetic rubber-like material and projects from the exterior surface of the drum to the walls of the mined area. Thus, as the drum rotates, the intermediate spiral will flex against the surface of the mine walls so as to "sweep" fine coal particles therefrom in order to maximize coal recovery. The intermediate spirals can be continuously arranged on the exterior surface of the drum or, alternately, could be periodically placed therealong in a spiral arrangement. If the later arrangement is chosen, it is preferable to utilize flexible, yet durable bristles such as metal or synthetic fiber bristles.
Preferably, the rotating drum is supported about a hollow shaft through which a liquid, preferably water, may be injected under pressure. The water travels through the hollow shaft and exits at the central portion of the cutting bit so as to aide the cutting bit in its removal of coal particles. The spent water which has been injected through the shaft may then be picked up by the recovery apertures. This is especially true if a flexible intermediate spiral is used so that a sealing effect is maintained with the walls of the mine. Thus, even though water may be injected into the mine shaft, the extent of water flow therein can be controlled by utilizing the present invention. As such, the present invention acts somewhat like a "pump" to transfer the water injected towards the front of the drilling head and encourage it to move in the interior portion thereof towards the rear where it can then be transferred to any suitable location. Additionally, the use of water greatly facilitates the removal of coal from the mine since a slurry mixture of coal particles and water will be effected. Thus, such slurry mixture may be removed from the mined area utilizing the present invention.
A fan turnable by the rotational movement of the shaft may be provided to effect air flow in a rearward direction. In such a manner, the fan can be provided to entrain fine particles of dust, for example, coal dust, and thereby maintain the quality of atmosphere in a mine shaft according to applicable standards. The rotating drilling head according to the present invention can be adapted to be utilized by any conventional power driven means.
Thus, it is primary object according to the present invention to provide a rotatable drilling head which can be advantageously utilized with conventional power driven means and which can be used to increase the recovery of coal, for example, mined underground. It is also an object of the present invention to provide a rotatable drilling head which is capable of decreasing toxic dust and/or particles which may exist by virtue of mining operations.
These and other objects of the present invention will become more apparent to one in the art after thorough consideration is given to the detailed description of the invention which follows.